I think it is the silver colour of the 'tracks' themselves that are strange to you.
You are used to seeing the darker grey or black plastic colour.Take the the tracks off the Panzer IV and just make sure that they aren't oiled or greased in any way. They almost certainly are just dry metal,so simply spray them with matt black rattle can paint.
Any kind will do, I have always used a cheap car paint. Let it dry and put them back on. A few trips along a rough surface like concrete or tarmac will very quickly scratch the paint off the raised portions of the tread and the tracks will look much better. Try to stay away from adding rust colours....most metal that moves especially over rough ground will very quickly be scoured free of rust by the abrasive nature of the ground. Muddy yes, rusty no, unless it is a wreck!
For a better look,you could collect some fine dust or get a mud coloured chalk stick, scrape, or grind a piece, to break it down into a fine powder and just gently 'blow' some onto the wet black paint.
Alb.
